Recent work has shown that an increase in the biomechanical loading of the temporomandibular joint (TMJ) stimulates cellular proliferation and cartilage formation from the undifferentiated mesenchymal layer, resulting in thickening of the soft tissue layers and associated remodeling of subarticular hard tissues. This contributes to the development of deviations in form of the temporal component and of the condyle, with secondary changes in the articular disc. These changes can impede the function of the TMJ and are likely to be associated with TMJ pain and tenderness. Although these changes and their significance have been described for older age groups, little is known about their occurrence in young adults, who comprise a large portion of clinical populations with subjective TMJ symptoms. The purpose of this proposal is to study and quantitate pathoanatomic changes in the temporomandibular joints of young adults (17-37 years) and to estimate the association of these changes with features of their dental occlusion which are presumed to cause adverse loading. 150 TMJs are being procurred en bloc from young adults at post mortem, and will be studied to evaluate the following: 1) anatomical and radiographic characteristics, 2) macroscopic characteristics to identify deviations in form, changes in surface color, lesions of the articular surfaces and secondary changes in the structure of the articular disc and its attachments and 3) microscopic characteristics; a) 100 sets of dissected joint components will be studied to observe the variation in thickness and structure of the hard and soft tissue layers (paraffin technique), b) 50 intact TMJs will be studied regarding the interrelationships between joint components, innervation, and vascularization (celloidin technique). These investigations will be pursued as indicated to develop a more complete understanding of the intracapsular mechanisms underlying temporomandibular pain and dysfunction which have not been adequately explained in the age group to be sampled. Further, the proposed study is intended to yield information that will direct clinicians towards dental treatment aimed at interrupting the derangement and deterioration of the temporomandibular joint.